Pressure gauge



P. MONDET PRESSURE GAUGE May 13, 1952 2 SHEETSSHEET 1 Filed April 21,1950 JNVENTOR. \MM uh P. MONDET PRESSURE GAUGE May 13, 1952 2SHEETS-SHEET 2 Filed April 21, 1950 INVE TOR.

Patented May 13, 1952 2,596,271

UNITED STATES PATENT OFFICE PRESSURE GAUGE Paul Mondet, Lyon, France,assignor to Ateliers Ventil, Lyon, France, a, French joint-stock companyApplication April 21, 1950, Serial No. 157,270 In France February 14,.1950 3 Claims. (Cl. 73-392) My invention relates to pressure gaugeswhere- Fig. 9 is a large scale view showing the optical in there is useda liquid such as waterimage of the electric bulb on the meniscus as itIn such pressure gauges the difference between appears in the telescope.the pressure to be measured and the outer at- The apparatus illustratedin Fig. 1 comprises mospheric pressure causes a corresponding. difa baseI supported by a fixed support 2 and by ference in the level of theliquid in the glass tube two levelling screws 3. Base I is integral withof the gauge. The variation of this level may be a reservoir 4 whichcontains the liquid ensuring measured by optical means ensuring a highdeoperation of the gauge, for instance water. Resgree of precision. Thediificulty is that the upper ervoir 4 has a comparatively largehorizontal secsurface of the liquid within the tube is not a geoi9 tionin such a manner that the inner water level metrical plane but a concavesurface or meniscus; therein is only slightly affected by the variationsthe upper limit of this meniscus cannot be asof the water level in theglass tube. The residual certained and the lowermost point thereof(ceninfluence may easily be taken into account by ter of the meniscus)is not clearly visible in a properly graduating the scale of theapparatus, horizontal sighting telescope. This drawback as it wi11 bereadily understood. Reservoir 4 is limits the possibilities of this typeof pressure tightly closed by a cover 5 which is soldered in gauge.position. Cover 5 carries a small Water level 6 A first object of myinvention is to provide to permit of properly levelling the apparatus.means whereby the position of the meniscus in The effective volume ofreservoir 4 is reduced the glass tube of the gauge may be ascertained.20 to a minimum by inner projections such as 1 without any diificultyand without any risk of (Fig. 3) which however do not reach the normalerror even by a comparatively untrained cperalevel of water within thereservoir. tor'. Base I carries laterally of reservoir 4 a hollowAnother object of my invention is a pressure vertical cylindrical column8 of relatively large gauge of the liquid type wherein the lower facediameter (Fig. 3). Column 8 is closed at its upof the meniscus in theglass tube is used as a per end by a cover 9 in which there is formed aconvex mirror to form an optical image of a small inner chamber tightlyclosed by an upper light source disposed at a definite distance belowcap II]. the meniscus and laterally of the glass tube, the Within column8 there is provided a vertical said image being observed in a horizontalsightr tube I I made of a transparent material such as ing telescopevertically displaceable along the glass and which is intended to formthe so-called said glass tube. glass tube of the gauge. The upper end oftube Still a further object of my invention is a pres- I I is passedthrough a packing gland I2 and opens sure gauge comprising a liquidreservoir, a verinto the inner chamber of cover 9, while its lower ticalglass tube in communication with this resend is similarly passed throughanother packing ervoir, a carriage vertically slidable along the glandI2 and opens into a small chamber I3 in said glass tube, a sightingtelescope horizontally base I, the said chamber I3 being closed by acarried by the said carriage to permit observalower cap I4. It will beunderstood that caps Ill tion of the glass tube, and an electric bulbalso and I4 give access to both packing glands I2 and carried by thesaid carriage below the plane of 410 permit of easily replacing tube IIwhen necesthe telescope and. on the opposed face of the glass sary.

tube with respect to the said telescope to form Chamber I3 communicateswith a horizontal on the lower face of the liquid meniscus withinconduit I5 provided in base I and this conduitis the glass tube anoptical image which may be connected by a passage It with the lower partof seen in the lunette. reservoir 4. Between the said conduit I5 and In.the annexed drawings: passage Iii there is interposed an adjustable Fig.l is a general plan view of my improved damping valve II formed by theconical end of a pressure gauge, with partsin section through line rod2!]- which is screwed in a sleeve 2| having an of outer screw-threadedperiphery. Sleeve 2| is in Figs. 2. 3 and d are sections taken alonglines turn screwed in a screw-threaded bore provided 11-41, III-III and(Fig. l). in base I in line with respect to conduit I5. A s. 5, 6. and 7re ection taken l ng lines packing gland 22 is disposed around rod 20,such VIVI and VII--VII (Fig. packing gland being pressed by means ofsmall 8 a diagrammatical view illustrating the longitudinal rods 23which are passed through operation of the gauge. sleeve 2|, these rods23 being in turn pressed by a ring 24 screwed in the bore of base 5. Anouter knob 25 permits actuation of valve [1.

Base l supports a vertical tube 26 which opens within reservoir 4immediately below cover 5. Tube 26 communicates with a lateral nozzlez'i(Fig. 1) by means of which the upper space of reservoir 4 may beconnected either with the outer atmosphere or with a tube, tank or otherclosed space within which a positive pressure is to be measured, asexplained below.

The inner chamber provided in cover 9 under cap I!) is connected by avertical tube 28 with a horizontal conduit 29 provided in base I, suchconduit communicating in turn with a second lateral nozzle 36 (Figs. 1and 2) by means of which the upper end of tube ll may be connectedeither with the outer atmosphere or with a tube, tank or like closedspace within which a negative pressure is to be measured. As shown inFig. 2, tube 28 extends through column 8 in parallel relation to tube Il.

Nozzles 27 and 36 are preferably constructed as indicated in Fig. 2, bymeans of an outer blind sleeve opening outwardly and formed with aninner tube 30a of short length. It will be understood that when a rubberhoseis engaged into such a nozzle, tube 36a. is forced into the hosewhile the latter is prevented against radial expansion by the inner wallof sleeve 36. There is thus easily obtained an air-tight connection.

It will be noted that tube 28 (Fig. '7) supports two insulating washers3| which carry a metallic tube 32 extending from base I to cover 9. Asit will be hereinafter explained, tube 32 is used to transmit electriccurrent to themovable carriage of the gauge.

The above-described conduit l communicates with a conduit 33 (Figs. 3and 4) which in turn communicates with a vertical pipe 34 disposedlaterally with respect to reservoir 4. Pipe 34 is closed by means of acap 35 and it is used for filling theapparatus. Conduits l5 and 33 areslightly sloping in such a manner that air bubbles -may escape freelyduring the filling operation either towards reservoir 4 orltowards pipe34. A removable valve cap 36 (Fig. 4) is provided to permit access toconduit 33. The height of pipe 34 is such as to exactly correspond tothe'normal level of liquid within reservoir 4, in such a'mannerthat allthe operator has to do to fill the auge is to pour liquid until thelevel reaches the upper end of the filling pipe.

Column 8 carries a vertical screw 31 (Fig. 3) supported at both ends byball bearings 33 respectively carried by base I and by cover 9. Thelower end of screw 31 carries a bevel pinion 39 which meshes with abevel gear 46 carried by a horizontal shaft 4| rotatably supported bybase I, such shaft 4| being provided with an outer actuating knob 42.

Column 8 is formed with a longitudinal slit through which there ispassed an arm 43 (Fig. 1) integral with a carriage 44 carrying twoscrewthreaded rings 45' (Fig. 2) adapted to form nuts on screw 31. Anylongitudinal play between carriage 44 and screw 3'! is taken up bydevices not shown, and which may be or" any description, for instance ofthe kind used in the construction of machine-tools. Arm 43 is alsoprovided with spring-pressed balls adapted to bear on the edges of thelongitudinal slit of column 8. One of these spring and ball devices hasbeen illustrated in Fig. 1, the ball being referenced 46 and. the spring41; it will be easily understood that a similar device is provided toco-act with the opposed edge of the slit. This arrangement enables arm43 and carriage 44 to move vertically along column 8 without howeverrotating about the axis of screw 31. The outer end of arm 43 supports ahorizontal lug 48 (Fig. 2) carrying a vertical pivot 49 integral withthe support 56 of a horizontal sighting telescope 5|. A spring and balldevice 52-53 forms an elastic lock whereby telescope 5| is retainedeither at the position at which it is pointing towards tube H throughthe slit of column '8, or at a position at right angles to the firstone, this second position being used to reduce the overall dimensions ofthe apparatus when the latter is not in use.

Carriage 44 also supports an arm 54 (Figs. 1 and 2) carrying at its freeend a socket 55 for a small low-voltage electric bulb 56 disposed closeto tube ll. One of the terminals of bulb 56 is grounded while the otheris connected to a small spring-pressed brush 51 movable in an insulatingsocket 58 supported by carriage 44, the said brush being adapted toslidably bear against the insuiated tube 32. The lower part of column 8has an openable window 80, to permit easy access to bulb 55.

Base 1 carries a horizontal tube 59 (Fig. 5) enclosing two cylindricalelectric cells 60 disposed in opposed relation eachside of a centralcontact 61 against which they are pressed by springs 62 bearing againstremovable caps 63. It will be understood that the anodes of'cells 60 arethus connected in parallel by means of contact 6!, while springs 62 forma connection between the cathodes of cells 66 and base l. Contact 6! isconnected to a switch 64 which is in turn connected with tube 32.

Arm 43 (Fig. 2) is provided with a vertically elongated opening in whichthere is slidably disposed a small carriage 65 actuated by a verticalscrew 56 having a lower actuating knob 61. Carriage 55 supports aVernier 68 adapted to slide along a scale 69 fixed to column 8., A lens39 isrcarried by Vernier 68 to facilitate readings.

The gauge above-described is used as follows:

Reservoir 4 is first filled with an appropriate liquid, for instancewater. Nozzles 21 and 30 being both open carriage 44 is lowered towardsthe lower part of scale 63'. The operator then observes the water levelin tube ll through telescope 51. Referring to Fig. 8 it will be seenthat light rays from bulb 56 pass through the wall of tube ll, strikethe lower face of the meniscus M and are reflected towards telescope 5|.If the latter is properly positioned the operator should therefore seethe optical image of the filament of bulb 56. In actual practice thisimage is strongly deformed and owing to parasitical refiections a secondor parasitical image is also visible in such a manner that, if bulb 56is properly adjusted, there appears in telescope 5| a pair of luminouslines A and B '(Fig. 9) horizontally disposed one above the other.Carriage 44'is then displaced by means of knob 42 until the morebrilliant of lines A and B is in coincidence with the horizontal wire Hof the reticle. Knob 61 is thereafter actuated to bring the zero ofVernier E8 in exact coincidence with the zero of scale 69. The gauge isthen ready for use. i

In order to measure a positive pressure, nozale 2! (Fig. 1) is connectedto the space within which this pressure is to be measured. The air orother gas under pressure thus acts through tube 25 on the water levelwithin reservoir 4 and the level rises in tube II Knob 42 is thenactuated and carriage 44 is raised until line A is again in coincidencewith the horizontal wire of telescope 5|. The height of water ormanometric head corresponding to the positive pressure to be measured isthen directly read on scale 69 by means of vernier 68. If, as it oftenoccurs, the water level within tube H is not steady but oscillatesirregularly, these oscillations are easily damped by progressivelyclosing valve 11 (Fig. 3) by means of knob 25 until a correctobservation is possible.

When a negative pressure is to be measured, nozzle 2'! is left open tothe outer atmosphere and nozzle 30 is connected with the tube, pipe,container or like closed space Within which the pressure is to bemeasured. Water rises in tube ll under the suction effect thus producedat the upper end of the said tube and the manometric head correspondingto the pressure to be measured is determined as above explained.

It will be observed that for any position of carriage 44 the verticaldistance between bulb 56 and the meniscus M remains constant, whatevermay be the height of column 8 and of screw 31. The luminosity of theimages observed in the telescope is thus constant and the telescope isadjusted once for all for the distance of the virtual image formed inthe meniscus.

It will be understood that my invention is in no way limited by theabove description. The glass tube such as H in which the liquid risesunder the action of the pressure to be measured will generally bevertical, but in some instances it may be more or less oblique, in whichcase the movable carriage should move obliquely along the tube. Also itis of advantage that the telescope should be arranged horizontally toobserve the image of the bulb in the meniscus, but it could as well bedisposed obliquely.

I claim:

1. A pressure gauge comprising a base; a reservoir carried by said baseand containing a transparent liquid; a vertical tubular column carriedby said base, said column being formed with a vertical slit; 2. cover atthe upper end of said column, said cover being formed with an innerchamber; a vertical transparent tube extending within said column fromsaid base to said cover, the lower end of said tube being incommunication with said reservoir and the upper end of said tube openinginto said chamber; a second tube extending vertically within said columnfrom said chamber to said base, the lower end of said tube being incommunication with a nozzle carried by said base and adapted forconnection with a space wherein a negative pressure is to be measured; asecond nozzle carried by said base and communicating with the upper partof said reservoir, said second nozzle being adapted for connection witha space wherein a positive pressure is to be measured; a verticalrotatable screw extending within said column; means on said base tomanually rotate said screw; a carriage carried by said screw and havingscrewthreaded portions engaging the screw threads thereof, said carriagebeing formed with an outwardly extending arm passing through said slitto be guided thereby; an electric bulb supported by said carriage inclose proximity of said transparent tube and adapted to illuminate thelower face of the meniscus formed by said liquid in said transparenttube for a proper position of said carriage; a horizontal sightingtelescope supported by the outer end of said arm above said bulb andadapted for observation through said slit of the image of said bulbformed by the lower face of said meniscus; a vertical metallic tubedisposed on said second-named tube but electrically insulated therefrom;brush means carried by said carriage in insulated. relation thereto,said brush means being electrically connected with said bulb; and meansto supply electric current to said last-named insulated tube.

2. In a pressure gauge as claimed in claim 1, said column carrying avertical scale and said arm supporting a Vernier adapted for cooperationwith said scale.

3. In a pressure gauge as claimed in claim 1, liquid damping meansinterposed between said reservoir and said transparent tube.

PAUL MONDET.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,091,303 Brelsford Aug. 31, 19372,197,205 Cooper Apr. 16, 1940 2,496,447 Dresser Feb. '7, 1950 FOREIGNPATENTS Number Country Date 895,939 France Apr. 17, 1944

